Why do whiteT-shirts turn yellow in the sun?Why do blackT-shirts fade in the sun?Why do old newspapers turn Y

Question

Y means yellow at the end

Answer 1

Sun light contains ultraviolet radiation which affects chemicals in different ways.

On dyes and paints it has a bleaching effect breaking down the complex colour molecules, but for natural plant fibres, it acts on lignin (the glue in the plant cells) to reactiveate the colour (yellow) As newsprint is not expected to be kept for long, the lignin is not removed from the wood fibre, and even without the sun, the paper will slowly turn yellow. Xerox paper has had nearly all the lignin removed from the fibre, and so does not turn yellow very easily. (The coating of clay and starch also helps)

Answer 2

because of a build up of dirt. white dirt particles make black fade in colour, and white t-shirts and newspapers turn yellowish because of dust and dirt..overtime.

Paper is made from wood, which is made up mainly of white cellulose. Wood also has a lot of a dark substance in it called lignin, which ends up in the paper, too, along with the cellulose. The exposure of lignin to air and sunlight is what turns paper yellow.

Newsprint, which must be produced as economically as possible, has more lignin in it than finer papers. At the mill, the wood that will be turned into newsprint is ground up, lignin and all.

Lignin eventually turns paper yellow because of oxidation. That is, the lignin molecules, when exposed to oxygen in the air, begin to change and become less stable. The lignin will absorb more light, giving off a darker color. Chang says that if newsprint were kept completely out of sunlight and air, it would remain white. After only a few hours of sunlight and oxygen, however, it will start to change color.

Launder shirts frequently, especially polyester blends and garments that might be affected by deodorants or anti-perspirants. Polyester absorbs oily soils readily but does not like to give them up. Yellowing can occur over time if soils are not completely removed. Also, white shirts may grey over time if laundry detergents build up, so thorough rinsing is important during the laundry process.

Anti-perspirants and deodorants as well as perspiration, itself, weaken cotton fibers. Fabrics may turn yellow in affected areas and may actually become brittle and tear. Wash garments soon after wearing to remove these substances.

Chlorine bleaches cause yellowing of white shirts that have optimal brighteners put on them to keep them looking white. Also, finishes on interfacings and some permanent press finishes are "chlorine-retentive" and cause similar yellowing. This problem usually cannot be reversed.